1. Field of the Invention
The present invention relates to a lacquer formulation comprising a surface-modified silicon dioxide and having improved performance properties, and to its use.
2. Discussion of the Background
Clearcoat materials are extensively employed industrially for coating a very wide variety of surfaces, such as those of wood, plastics or metals, for example (Ulmann, 4th edition, volume 15, p. 589 ff.). Since generally the intention is that the surface of the coated article should be readily recognizable, the transparency of such coating materials is one of their most essential properties. The surfaces to be coated often have a high gloss. In many cases, therefore, the coating material is subject to the requirement that the surface should appear matt. This can be achieved through the addition of matting (or flatting) agents, which are incorporated into the clearcoat material.
These matting agents are composed of natural materials or are prepared synthetically. They are in the form of fine particles (approximately 1 to 30 μm) and ideally have the following properties: high pore volume, narrow particle distribution, suitable particle size, tailored to the respective application, and narrow pore distribution. Matting agents commonly employed include silicas (both precipitated silicas and silicas prepared on the basis of pyrogenic silicas) and/or silica gels.
When matting agents are used a problem which may occur is that the transparency of the clearcoat material is adversely affected in accordance with the particle size and refractive index both of the coating material and of the matting agent. This becomes particularly apparent when the clearcoat material is applied to a glossy black substrate. If transparency is poor the black surface appears to the viewer to be grayish, which is an unwanted phenomenon in application.